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Emerald Group Publishing Limited
Copyright © 1998, MCB UP Limited
Keywords Lasers, Position, Sensors
Sensing the exact position of small, fast-moving object is the mission of the OHDM 16 laser-beam photoelectric sensor developed by Baumer Electric Ltd in Southington, Connecticut. This capability suits high-precision applications such as monitoring the position of miniature drill bits and other machine-tool components. The new sensor also helps semiconductor manufacturers accurately count the number of wafers inside a carrier, whereas previous-generation laser sensors were hampered by the selective characteristic of silicon wafers. The OHDM 16 can be set up to operate 20 to 100mm from the target surface with an optimum sensing distance of 80mm, depending on the space requirements of the sensing application. The device emits a visible red laser beam from its miniature diode that will contact target objects. The beam is reflected back to two receivers on the instrument's sensing face. The electronics within the sensor housing use triangulation to accurately detect a target, while a lens system eliminates any background interference. The new OHDM sensor can detect objects as small as 0.1mm with a response time of less than 0.6 microsecond, enabling it to detect fast-moving objects, such as drops of liquid or a thread. Its low-power, class 2 laser diode increases the instrument's working life, which is specified to be approximately 10,000 hours at ambient temperature of less than 40°C.